ORNL-CF-59-1-13.txt

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59 - 1 - 13
REVISED
" DATE:  February 24, 1959 copy no. 6/
SUBJECT: Fuel Cycle Costs in a Graphite Moderated Slightly
Enriched Fused Salt Reactor
TO: Distribution
FROM: C. E. Guthrie 7
. Abstract
. ooty
.
;- A fuel cycle economic study has been made for a
e 315 Mw, graphite moderated slightly enriched molten

salt fueled resctor, Fuel cycle costs in the order
of 3.3 mills/kwh were calculated for the throw-away
cycle. Recovery of the uranium and plutonium at the
end of the cycle reduces the cycle costs to ~1.6
mills/kwh. Changes in the waste storage and reproc-
essing costs have a relatively minor effect on fuel
cycle costs.

RELEASE APPROVED
NOTICE BY PATERI BR G}:’

This document contains information of a preliminary é’z’fi.—é —Q) Somiiin A

nature and was prepared primarily for internal use DATE
at the Oak Ridge National Laboratory. [tis subject
to revision or correction and therefore does not
represent a final report.

 

S
1

reprinted or fl!;herW‘so given publi
UNGLASSI F I En mthout thc appflava} of the ORNL patent ek,
afermation Centrel Departasent.
-

*
* -

Foreword

This revision incorporates more accurate nuclear calculations and
some changes in economic basis.

Introduction

One potential advantage of a fluld fueled reactor is a low fuel cycle
cost, There are two alternate approaches, both unique to the fluid fuel
concepts, one might take to realize this potential: (1) continuous reproc-
essing, thereby keeping the poisons at a minimum and the conversion (or
breeding) ratio at a maximum, or (2) continuous additions of enriched fuel
(to make up for burnout and reactivity decrease), thereby attaining very
high burnup on the original fuel charge. The latter approach is the one
more aggéic&ble to the fused salt (LiF, BeF, UFy) reactor operating on the
U235. cycle., Yor fused salt reactors operating on the Th-U cycle
either approach can be used since the volatility process could be used to
continuously {(or semicontinuocusly) recover the U-235 and U-233.

This study has been made to determine the range of fuel cycle costs
anticipated for _a graphite modersted fused salt burner reactor operating
on the U235~Ua38 cycle. The nuclear calculations and cycle costs for the
Th-U23> cycle will be worked out and reported at a later date.

Reactor Basls*

The resctor considered is graphite moderated with a fluid fuel consist-
ing of a molten mixture of lithium~7 fluoride, beryllium fluoride and
slightly enriched uranium fluoride. During the reactor cycle highly
enriched UF) 1s added to the system to supply burnup and meke up for the
reectivity loss due to accumilated fission products. The inventory of
Tissile 1sotopes In the reactor and the U-235 additions as a function of
time are shown in Figs. 1 and 2, respectively. The other reactor parameters
are:

775 Mw Thermal

315 My Electrical

900 £t3 Fused Salt inventory

80% Load Factor

1.4% Initisl U-235 Enrichment
20% UF), Salt Composition, Mole %
70% LiY%

10% BeF,

 

*A1l reactor data supplied by L. G. Alexander from ORACLE calculations.
 

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Economic Basis

Two fuel cycle cases have been considered, both of which assume no Li-T
recovery. In each case the cycle repeats by the reactor being fueled with
fresh salt containing 1.4% enriched U.

1) Throw-away cycle - At the end of the reactor cycle (or lifetime) the
regetor salt inventory including fisslionable isotopes would be discarded

into on-site waste tanks for permanent storage. A $1,000,000 investment

has been assumed at the end of the cycle for a storage facility and provision
for permanent monitoring.

2) U and Pu recovered at end of cycle by solvent extraction - Recovery
costs of $150/kg U (representative of current technology and scale of
processing) and $50/kg U (large scale technology) have been estimated.

The economics were calculated on the following bhasis:

Salt cost $1700/ft3 (excluding U value).

U value at officisl price schedule.

Pu credit $15/gm of Pu-239 and Pu-24l,

% use charge was paid on initial loading of U, U-235
added during cycle, and Pu buildup during the cycle,
A 5% interest sinking fund was used to pay for
either U discard and storage costs or processing
costs at the end of the cycle and to take care of
increasing use charges.

The investment in salt was payed off over the cycle with
a 10% return (before taxes).

Results

The fuel cycle costs, claculated for each case as a function of cycle
time, are shown in Fig. 3. A minimum fuel cycle cost of 1.6 mills/kwh
is predicted for a reactor cycle of 4.5 years when the U and Pu are recovered
at the end of the cycle for $50/kg U. For $159/kg U recovery costs, cycle
costs are essentially constant at ~2 mills/kwh for cycles in excess of 5
years, In all cases it pays to recover the U and Pu at the end of the cycle
since the minimum throw-away cycle cost is 3.35 mills/kwh. Tgble I shows a
breakdown of the costs for the five-year cycle.

Errors in the fused salt waste disposal and initial salt costs have
little effect on the fuel cycle costs for cycles 5 years or longer.
Increasing the waste disposal cost by $1,000,000/cycle and the salt cost
by $1000/ft3 would increase the five-year cycle costs by 0.08 mill/kwh and
0.12 mill/kwh respectively. Changing the return on salt investment to 12%
and the interest on sinking fund to 6% (instead of 10% and 5%) would decrease
P
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Table I

Five-~Year Cycle Cost Breakdown

 

 

 

Throwaway Recovery Cycle
Cycle $50/kg U $150/kg U

 

Use Charge on Initial U Loading 0.13 Mills/kwh 0.13 Mills/kwh 0.13 Mills/kwh
Use Charge on U-235 Added and

Pu Buildup 0.29 0.29 0.29
Salt Amortization 0.21 0.21 0.21
Burnup 0.79 0.79 0.79
Fuel Throwaway Cost 1.84 - -
Waste Storage for Throwaway 0.08 - -
Reprocessing Charges - 0.23 0.69
Total Cycle Costs 3.34 Mills/kwh 1.65 Mills/kwh 2,11 Mills/kwh

 

the cycle cost by 0.01 mill/kwh for the 5-year cycle and by 0.15 mill/kwh
for the ll-year cycle,

It is interesting to compare these fuel cycle costs, which are for
a single reactor with present reprocessing technology, with the fuel cycle
costs anticipated for solid fueled reactors at the present tim?. Two such
reactors which are typical are the Yankee w}th e 7.1 mills/kwh 1) fuel cost
and the Indian Point with a 5.8 mills/kwh(2) fuel cost. These costs will
be reduced by the mass production of fuel elements and large scale reproc-
essing possible in a large nuclear economy. It will probably take, however,
a nuclear economy in the order of 105 Mw, (1980-2000) to reduce solid
fueled reactor fuel cycle costs to 1.5 mills/kwh. As far as fuel cycle
costs are concerned slightly enriched fused salt reactors appear to be
superior at present and competitive in the future to heterogeneous reactors.

 

(l)Schoupp, W. E., Advanced Pressurized Water Systems Proceedings of Atomic
Energy Management Conference, March 17-19, 1958, Chicago, Ill., p. 142.

(2)3. Fe Fairman, Estimated Costs of Indian Point Nuclear Power Plant, Ibid,
p. 357.
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